Toxicology for Judges – The New Reference Manual on Scientific Evidence (2011)

I have begun to dip into the massive third edition of the Reference Manual on Scientific Evidence.  To date, there have been only a couple of acknowledgments of this new work, which was released to the public on September 28, 2011.  SeeA New Day – A New Edition of the Reference Manual of Scientific Evidence”; and David Kaye, “Prometheus Unbound: Releasing the New Edition of the FJC Reference Manual on Scientific Evidence.”

Like previous editions, the substantive scientific areas are covered in discrete chapters, written by subject matter specialists, often along with a lawyer who addresses the legal implications and judicial treatment of that subject matter.  From my perspective, the chapters on statistics, epidemiology, and toxicology are the most important in my practice and in teaching, and I decided to start with the toxicology.  The toxicology chapter, “Reference Guide on Toxicology,” in the third edition is written by Professor Bernard D. Goldstein, of the University of Pittsburgh Graduate School of Public Health, and Mary Sue Henifin, a partner in the law firm of Buchanan Ingersoll, P.C.


At the question and answer session of the public release ceremony, one gentleman rose to note that some of the authors were lawyers with big firm affiliations, which he supposed must mean that they represent mostly defendants.  Based upon his premise, he asked what the review committee had done to ensure that conflicts of interest did not skew or distort the discussions in the affected chapters.  Dr. Kassirer and Judge Kessler responded by pointing out that the chapters were peer reviewed by outside reviewers, and reviewed by members of the supervising review committee.  The questioner seemed reassured, but now that I have looked at the toxicology chapter, I am not so sure.

The questioner’s premise that a member of a large firm will represent mostly defendants and thus have a pro-defense  bias is probably a common perception among unsophisticated lay observers.  What is missing from their analysis is the realization that although gatekeeping helps the defense lawyers’ clients, it takes away legal work from firms that represent defendants in the litigations that are pretermitted by effective judicial gatekeeping.  Erosion of gatekeeping concepts, however, inures to the benefit of plaintiffs, their counsel, as well as the expert witnesses engaged on behalf of plaintiffs in litigation.

The questioner’s supposition in the case of the toxicology chapter, however, is doubly flawed.  If he had known more about the authors, he would probably not have asked his question.  First, the lawyer author, Ms. Henifin, is known for having taken virulently anti-manufacturer positions.  See Richard M. Lynch and Mary S. Henifin, “Causation in Occupational Disease: Balancing Epidemiology, Law and Manufacturer Conduct,” 9 Risk: Health, Safety & Environment 259, 269 (1998) (conflating distinct causal and liability concepts, and arguing that legal and scientific causal criteria should be abrogated when manufacturing defendant has breached a duty of care).

As for the scientist author of the toxicology chapter, Professor Goldstein, the casual reader of the chapter may want to know that he has testified in any number of toxic tort cases, almost invariably on the plaintiffs’ side.  Unlike the defense lawyer, who loses business revenue, when courts shut down unreliable claims, plaintiffs’ testifying or consulting expert witnesses stand to gain by minimalist expert witness opinion gatekeeping.  Given the economic asymmetries, the reader must thus want to know that Prof. Goldstein was excluded as an expert witness in some high-profile toxic tort cases.  See, e.g., Parker v. Mobil Oil Corp., 7 N.Y.3d 434, 857 N.E.2d 1114, 824 N.Y.S.2d 584 (2006) (dismissing leukemia (AML) claim based upon claimed low-level benzene exposure from gasoline) , aff’g 16 A.D.3d 648 (App. Div. 2d Dep’t 2005).  No; you will not find the Parker case cited in the Manual‘s chapter on toxicology. (Parker is, however, cited in the chapter on exposure science.)

I have searched but I could not find any disclosure of Professor Goldstein’s conflicts of interests in this new edition of the Reference Manual.  I would welcome a correction if I am wrong.  Having pointed out this conflict, I would note that financial conflicts of interest are nothing really compared to ideological conflicts of interest, which often propel scientists into service as expert witnesses.


One way that ideological conflicts might be revealed is to look for imbalances in the presentation of toxicologic concepts.  Most lawyers who litigate cases that involve exposure-response issues are familiar with the “linear no threshold” (LNT) concept that is used frequently in regulatory risk assessments, and which has metastasized to toxic tort litigation, where LNT often has no proper place.

LNT is a dubious assumption because it claims to “known” the dose response at very low exposure levels in the absence of data.  There is a thin plausibility for genotoxic chemicals claimed to be carcinogens, but even that plausibility evaporates when one realizes that there are defense and repair mechanisms to genotoxicity, which must first be saturated before there can be a carcinogenic response.  Hormesis is today an accepted concept that describes a dose-response relationship that shows a benefit at low doses, but harm at high doses.

The toxicology chapter in the Reference Manual has several references to LNT but none to hormesis.  That font of all knowledge, Wikipedia reports that hormesis is controversial, but so is LNT.  This is the sort of imbalance that may well reflect an ideological bias.

One of the leading textbooks on toxicology describes hormesis:

“There is considerable evidence to suggest that some non-nutritional toxic substances may also impart beneficial or stimulatory effects at low doses but that, at higher doses, they produce adverse effects. This concept of “hormesis” was first described for radiation effects but may also pertain to most chemical responses.”

Curtis D. Klaassen, Casarett & Doull’s Toxicology: The Basic Science of Poisons 23 (7th ed. 2008) (internal citations omitted).

Similarly, the Encyclopedia of Toxicology describes hormesis as an important phenomenon in toxicologic science:

“This type of dose–response relationship is observed in a phenomenon known as hormesis, with one explanation being that exposure to small amounts of a material can actually confer resistance to the agent before frank toxicity begins to appear following exposures to larger amounts.  However, analysis of the available mechanistic studies indicates that there is no single hormetic mechanism. In fact, there are numerous ways for biological systems to show hormetic-like biphasic dose–response relationship. Hormetic dose–response has emerged in recent years as a dose–response phenomenon of great interest in toxicology and risk assessment.”

Philip Wexler, Bethesda, et al., eds., 2 Encyclopedia of Toxicology 96 (2005).  One might think that hormesis would also be of great interest to federal judges, but they will not learn about it from reading the Reference Manual.

Hormesis research has come into its own.  The International Dose-Response Society, which “focus[es] on the dose-response in the low-dose zone,” publishes a journal, Dose-Response, and a newsletter, BELLE:  Biological Effects of Low Level Exposure.  In 2009, two leading researchers in the area of hormesis published a collection of important papers:  Mark P. Mattson and Edward J. Calabrese, eds., Hormesis: A Revolution in Biology, Toxicology and Medicine (N.Y. 2009).

A check in PubMed shows that LNT has more “hits” than “hormesis” or “hermetic,” but still the latter phrases exceed 1,267 references, hardly insubstantial.  In actuality, there are many more hermetic relationships identified in the scientific literature, which often fails to identify the relationship by the term hormesis or hermetic.  See Edward J. Calabrese and Robyn B. Blain, “The hormesis database: The occurrence of hormetic dose responses in the toxicological literature,” 61 Regulatory Toxicology and Pharmacology 73 (2011) (reviewing about 9,000 dose-response relationships for hormesis, to create a database of various aspects of hormesis).  See also Edward J. Calabrese and Robyn B. Blain, “The occurrence of hormetic dose responses in the toxicological literature, the hormesis database: An overview,” 202 Toxicol. & Applied Pharmacol. 289 (2005) (earlier effort to establish hormesis database).

The Reference Manual’s omission of hormesis is regrettable.  Its inclusion of references to LNT but not to hormesis appears to result from an ideological bias.


One would hope that the toxicology chapter would not put forward partisan substantive positions on issues that are currently the subject of active litigation.  Fondly we would hope that any substantive position advanced would at least be well documented.

For at least one issue, the toxicology chapter dashes our fondest hopes.  Table 1 in the chapter presents a “Sample of Selected Toxicological End Points and Examples of Agents of Concern in Humans.” No documentation or citations are provided for this table.  Most of the exposure agent/disease outcome relationships in the table are well accepted, but curiously at least one agent-disease pair is the subject of current litigation is wildly off the mark:

Parkinson’s disease and manganese

Reference Manual at 653.  If the chapter’s authors had looked, they would have found that Parkinson’s disease is almost universally accepted to have no known cause, except among a few plaintiffs’ litigation expert witnesses.  They would also have found that the issue has been addressed carefully and the claimed relationship or “concern” has been rejected by the leading researchers in the field (who have no litigation ties).  See, e.g., Karin Wirdefeldt, Hans-Olaf Adami, Philip Cole, Dimitrios Trichopoulos, and Jack Mandel, “Epidemiology and etiology of Parkinson’s disease: a review of the evidence.  26 European J. Epidemiol. S1, S20-21 (2011); Tomas R. Guilarte, “Manganese and Parkinson’s Disease: A Critical Review and New Findings,” 118 Environ Health Perspect. 1071, 1078 (2010) (“The available evidence from human and non­human primate studies using behavioral, neuroimaging, neurochemical, and neuropathological end points provides strong sup­port to the hypothesis that, although excess levels of [manganese] accumulation in the brain results in an atypical form of parkinsonism, this clini­cal outcome is not associated with the degen­eration of nigrostriatal dopaminergic neurons as is the case in PD.”)


The substantive specialist author, Professor Goldstein, is not a physician; nor is he an epidemiologist.  His professional focus on animal and cell research shows, and biases the opinions offered in this chapter.

“In qualitative extrapolation, one can usually rely on the fact that a compound causing an effect in one mammalian species will cause it in another species. This is a basic principle of toxicology and pharmacology.  If a heavy metal, such as mercury, causes kidney toxicity in laboratory animals, it is highly likely to do so at some dose in humans.”

Reference Manual at 646.

Such extrapolations may make sense in regulatory contexts, where precauationary judgments are of interest, but they hardly can be said to be generally accepted in controversies in civil actions over actual causation.  Crystalline silica, for instance, causes something resembling lung cancer in rats, but not in mice, guinea pigs, or hamsters.  It hardly makes sense to ask juries to decide whether the plaintiff is more like a rat than a mouse.

For a sober second opinion to the toxicology chapter, one may consider the views of some well-known authors:

“Whereas the concordance was high between cancer-causing agents initially discovered in humans and positive results in animal studies (Tomatis et al., 1989; Wilbourn et al., 1984), the same could not be said for the reverse relationship: carcinogenic effects in animals frequently lacked concordance with overall patterns in human cancer incidence (Pastoor and Stevens, 2005).”

Hans-Olov Adami, Sir Colin L. Berry, Charles B. Breckenridge, Lewis L. Smith, James A. Swenberg, Dimitrios Trichopoulos, Noel S. Weiss, and Timothy P. Pastoor, “Toxicology and Epidemiology: Improving the Science with a Framework for Combining Toxicological and Epidemiological Evidence to Establish Causal Inference,” 122 Toxciological Sciences 223, 224 (2011).

Once again, there is a sense that the scholarship of the toxicology chapter is not as complete or thorough as we would hope.

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